I. Field of the Invention
The present invention generally relates to integrated passive devices fabricated utilizing organic laminates.
II. Description of Related Art
In recent times, voice communication has become just one of the myriad purposes for the transfer of radio Frequency (“RF”) data. An increasing number of bands, size reduction, integration, and refinements in design and fabrication technology have made it possible to pack more functionality into computing devices such as handhelds, gaming systems, broadcast units, global positioning units, satellite TV, last mile access, and radar units. It is becoming a reality that the market will soon demand cellular handsets with undropped calls over long coverage areas worldwide (using for, example, quadband GSM, WCDMA, TCDMA), that also are able to receive real-time entertainment from broadcast and satellite units, navigate using positioning systems, and connect seamlessly to the internet and local clients such as printers and scanners. In this scenario a single handheld, PDA or client such as laptop would have the following standards integrated (or comparable standards thereto): IEEE 802.11a/b/g WLAN (wireless local area network), LMDS/MMDS (local multipoint distribution system), satellite/digital TV (digital broadcasting service), UWB (ultra wideband), GPS (global positioning system) cellular and Bluetooth.
One of the initiatives to achieve such levels of performance, computing and connectivity was the integration of passive devices such as inductors, capacitors and resistors. Passive devices account for 75-85% of all components used in a cellular phone today. In comparison, only 15-25% of the components are active devices. Passive devices such as inductors, capacitors and transmission lines are combined to form filters, diplexer, multiplexers, duplexers, baluns, and couplers, which are utilized in multi-band RF systems. Thus, the size of these devices is very important to the viability of these multi-functional devices.
Currently, low-temperature co-fired ceramic (LTCC), multilayer ceramic (MLC), ceramic monoblock technologies, surface acoustic wave (SAW), and field bulk acoustic resonator (FBAR) are the prevalent technologies for the implementation of surface mount components such as front-end RF passive band pass filters, duplexers, multiplexers, couplers, and baluns. LTCC is a widely used ceramic technology because it uses miniature lumped components such as inductors and capacitors that can be optimized for operation over a wide band of frequencies, whereas monoblock, SAW, FBAR and MLC components use different materials for different frequencies and limits the integration of devices for multiband applications, which are required for different functions. Additionally, with the ability to integrate in excess of 20 layers, LTCC has become a desirable platform for the integration of front-end modules for multiband applications that combine several lumped element filters, baluns, couplers, multiplexers, matching circuits and diplexers for integrated multi-band, multi-standard applications.
It is typical for LTCC front-end modules to comprise more than 10-15 metal metallic layers with microvias connecting each layer, and in many instances also include SAW and FBAR filters mounted on the multiple ceramic layers to meet the more stringent requirements of bandpass filters. The need for many layers to provide the needed density translates to more design time and higher tooling cost and problems of shrinkage and performance issues. In addition, increases in density have been slow, and has not reached further than 75 components/cm2. To meet current density requirements, discrete components are mounted on the top surface of LTCC modules as discrete components. Besides the need for discretes to achieve the desired density or using thin film based devices, such modules have to be mounted on a printed circuit board (PCB). Further, LTCC also generally suffers from higher costs since it generally cannot be manufactured in panel sizes larger than 6×6 square inches. Moreover, LTCC generally has relatively low performance due to process tolerances and relatively high dielectric losses (e.g., tan δ=0.005-0.007 at 1 GHz).
Thus, there is an unsatisfied need in the industry for a high frequency, low loss, inexpensive filters, baluns, and diplexers having a relatively small footprint for multi-band, multi standard applications.